The present invention relates, in general, to the storage and retrieval of articles and, more particularly, to a document storage and retrieval system.
The need to retain or store documents has increased substantially in recent years. Governmental agencies are a prolific source of rules and regulations which require industry to maintain documentary evidence relating to an ever broadening range of subjects. Similarly, the exposure to litigation has increased almost everyone's need to retain documents. As the cost of space increases, particularly office space, there has been a tendency to move document storage to an off-site location or storage facility.
Since it is often not feasible for a company to store its documents in-house, document storage is frequently undertaken through a contractor at a storage facility at the periphery of an urban area. In recent years, therefore, document storage companies have come into existence and are operating storage facilities in which literally millions of documents are stored.
As the number of documents stored increases, the problems associated with storage and retrieval also increase. Small storage and retrieval contractors have simply tried to accumulate their various clients' documents in contiguous areas in the storage warehouse. As these systems increase in volume, the tendency has been to employ an approach similar to the warehousing of fungible products such as hardware, groceries or the like. Thus, the article is placed in a suitable container, and the container stored in a numbered location in the storage facility. If an article is to be retrieved, the container is recalled from the numbered storage location and the article removed from the container. The container will thereafter be returned to its numbered storage location, either without the article or when the article is a document, when the document is returned and refiled in the container. When this approach is employed, each location in the storage volume is given an identifying address and the container has an identifying indicia, often machine readable, which corresponds to the address.
The approach of assigning a constant address to a container is particularly suitable for use with fungible products. Thus, if the container is filled with bolts of the same size or cartons of laundry soap, removal of an article from the container does not pose a serious problem. The container can be replenished with articles soon after retrieval. Since each document generally will be unique, removal of a document from the container will usually result in the container with the remaining documents being pulled from the inventory of stored documents, which leaves a gap in the inventory that will remain until the container is replaced. As the volume of documents or containers increases, the number of gaps in the inventory of stored documents resulting from container retrievals dramatically increases. Thus, storage and retrieval systems which are based on constant addresses inherently do not maximize the density of the storage volume.
Various automated systems have been employed in an attempt to automate the storage and retrieval of documents and other articles. Typical of such automated systems are the apparatus and methods set forth in U.S. Pat. Nos. 4,285,623; 4,219,296; 3,536,194; 3,526,326; 3,531,002; and 3,482,712. While these automated storage and retrieval systems have devised certain scanning and container manipulating apparatus and controllers which greatly facilitate automation, they basically implement the automation by the use of a constant address system. Thus, to the extent that such automated storage and retrieval apparatus and methods are suitable for use with documents, they do not eliminate the problem of inefficient use of the storage volume by reason of gaps resulting when documents are retrieved.
An additional problem which results from assignment of a constant address to containers for documents or other articles is that the retrieval from the inventory of stored containers will tend to be somewhat random, with the gaps or locations not occupied in the storage volume being randomly distributed throughout the volume. Thus, the storage and retrieval equipment must operate throughout a greater storage volume, with the distance and time to store and retrieve documents being increased by the need for the equipment to pass beyond the various gaps in the storage volume. There is, therefore, no compaction of the volume toward the conveying equipment, and the path through which the containers must travel to be stored or retrieved can be minimized. The random empty locations in constant-address systems increases the inventory volume and causes the automatic conveying apparatus used to operate warehouse to move over longer and longer paths as the inventory volume increases. The density of the storage volume and its proximity to the automatic handling equipment in a constant address system is reduced by the retrieved containers.
In an inventory of one million containers, each filled with documents, a typical inventory handling rate would be about two percent per month, i.e., about 20,000 containers are handled with about 10,000 retrieved and about 10,000 stored. Of the 10,000 retrieved containers about 4,000 are forwarded back to the customer in their entirety and about 6,000 have one or more documents returned to the customer. When a document is pulled from a container, the container must be stored in a suspense storage volume or returned to the long term storage inventory. If the container is returned, it must be retrieved a second time and restored when the document is returned. This approach increases the handling rate by about 12,000 containers per month. If the 6,000 containers are stored in suspense storage, for example, for three months, the number of gaps in the long term inventory increases to 30,000 (assuming the 4,000 sent to the customers are also retained for three months).
In a constant address system, therefore, the container handling problems and the gaps in the long term inventory become substantial. Typically about one man per 11,000 containers or 90 men for a one million container inventory are required and the running volume of randomly distributed gaps can exceed 45,000 cubic feet.